1. Field of the Invention
The present invention relates to a connector device, and, in particular, to a connector apparatus including a jack connector for a balanced transmission system (differential transmission system) and a plug connector for a balanced transmission system (differential transmission system).
2. Description of the Related Art
As systems for data transmission, there are an ordinary transmission system (single-end system) and a balanced transmission system (differential transmission system). In the single-end system, a single electric wire is used for each data. In the balanced transmission system, a pair of electric wires are used for each item of data, a positive signal and a negative signal having the same amplitude and an opposite direction are transmitted simultaneously, and an electric potential difference between the positive and negative signals is used to transmit data. In the balanced transmission system, there is no influence from draft of a ground level, an advantage being that it is not likely to be influenced by noise in comparison to the ordinary transmission method, and thus, the balanced transmission system is used in many cases.
A connector is used to transmit data between two apparatuses. In a case where data is transmitted in such a balanced transmission system, a balanced transmission connector device having a structure such that a pair of transmission lines are provided for each item of data may be used. The balanced transmission connector device has a general configuration such that pairs of first and second signal contacts and sheet-shaped ground contacts are alternately arranged.
FIGS. 1A and 1B depict a portion of contacts included in a jack connector 10 and a plug connector 100 of a balanced transmission connector device in the related art.
In FIGS. 1A and 1B, X1-X2 directions denote row directions of an arrangement of contacts (width directions of the connectors), Z1-Z2 directions denote column directions of the arrangement of contacts (height directions of the connectors), and Y1-Y2 directions denote length directions of the connectors (depth directions of the connectors, or directions in which the connectors are inserted/removed therebetween).
The jack connector 10 is configured such that, sheet-shaped jack ground contacts 20 and pairs of first and second jack signal contacts 30, 40 are arranged thereon, and the jack connector 10 is mounted on a printed circuit board 200. Each of the jack ground contacts 20 has an upper arm part 22, a lower arm part 23 and a gulf part 24, and further, spring parts 25, 26 at an extending end of the jack ground contact 20.
The plug connector 100 is configured such that sheet-shaped plug ground contacts 120 and pairs of first and second plug signal contacts 130, 140 are arranged, an intermediate substrate 150 is connected with the plug ground contacts 120 and the first and second plug signal contacts 130, 140, and is provided to an end of a coaxial cable (not shown).
When the plug connector 100 is connected with the jack connector 10, as depicted in FIG. 1B, the first and second plug signal contacts 130, 140 in each pair come into contact with the first and second jack signal contacts 30, 40 in each pair, respectively, and each of the plug ground contacts 120 comes into contact with the spring parts 25, 26 of each of the jack ground contacts 20.
Because data signals transmitted by the balanced transmission connector 1 are radio frequency signals, the data signals are transmitted between the plug connector 100 and the jack connector 10 of the balanced transmission connector 1 which are connected together, while the data signals generate radio frequency ground currents in the plug ground contacts 120 and the jack ground contacts 20. Thus, the radio frequency ground currents flow through between the plug ground contacts 120 and the jack ground contacts 20.
The spring parts 25 and 26 of the jack ground contacts 20 provide returning paths for the radio frequency ground currents. The jack ground contacts 20 come into contact with the plug ground contacts 120 at almost extending ends of the spring parts 25 and 26, and therefore, so-called stubs are not formed. In contrast thereto, the plug ground contacts 120 have stubs 50 which are extending-side portions of the plug ground contacts 120 with respect to positions at which the spring parts 25 and 26 come into contact with the jack ground contacts 120. As can be seen from FIG. 1B, the positions at which the spring parts 25 and 26 come into contact with the jack ground contacts 120 are approximately the centers of the jack ground contacts 120 along the Y1-Y2 directions. Therefore, the stubs 50 have a length L1 which is relatively large.
The stubs 50 are such as to provide dead ends for the radio frequency ground currents, and thus, the radio frequency ground currents are reflected by the extending end of the stubs 50.
Patent Document: Japanese Laid-Open Patent Application No. 2000-068006
Recently, an information amount to be transmitted increases and a signal transmission rate is increased. Presently a transmission rate is on the order of around 2 Gbps, but a transmission rate is planned to be increased to the order of tens of Gbps in the next generation. When a signal is transmitted at a high transmission rate, a crosstalk characteristic, which is one of transmission characteristics of a balanced transmission connector device, may have to be improved, and for example, a crosstalk amount may have to be less than −30 dB, for the purpose of guaranteeing reliability in data transmission.
In FIG. 10, a graph line I depicts a crosstalk characteristic of a balanced transmission connector device 1 in the related art. As depicted in FIG. 10, in the graph line I, a crosstalk amount is not sufficiently reduced. This is because the above-mentioned stub 50 has a relatively large length L1.
Further, as depicted in FIG. 11, a graph line II, a crosstalk characteristic concerning resonance of the balanced transmission connector device 1 in the related art is such that, a crosstalk amount has a peak Q which occurs at a relatively low frequency.
It is noted that, in the above-mentioned crosstalk characteristic concerning resonance of the balanced transmission connector device 1 in the related art, in a case where data to be transmitted has a predetermined frequency, the ground contacts 20 and 120 resonate, radio frequency ground currents sharply increase, noise increases, the first and second signal contacts 30, 130, 40 and 140 are affected by the noise, and the crosstalk amount increases.
Therefore, in a case where a signal is transmitted at such a high transmission rate as tens of Gbps in near future, it may become difficult to guarantee reliability in data transmission.